The ability of crystalline alkali metal aluminosilicate (zeolite) to sequester calcium ions from aqueous solution has led to its becoming a well-known replacement for phosphates as a detergency builder. Particulate detergent compositions containing zeolite are widely disclosed in the art, for example, in GB 1 473 201 (Henkel), and are sold commercially in many parts of Europe, Japan and the United States of America.
Although many crystal forms of zeolite are known, the preferred zeolite for detergents use has always been zeolite A: other zeolites such as X or P(B) have not found favour because their calcium ion uptake is either inadequate or too slow. Zeolite A has the advantage of being a "maximum aluminium" structure containing the maximum possible proportion of aluminium to silicon--or the theoretical minimum Si:Al ratio of 1.0--so that its capacity for taking up calcium ions from aqueous solution is intrinsically greater than those of zeolite X and P which generally contain a lower proportion of aluminium (or a higher Si:Al ratio).
EP 384 070A (Unilever) describes and claims a novel zeolite P (maximum aluminium zeolite P, or zeolite MAP) having an especially low silicon to aluminium ratio, not greater than 1.33 and preferably not greater than 1.15. This material is demonstrated to be a more efficient detergency builder than conventional zeolite 4A.
U.S. Pat. No. 3,112,176 (Haden et al/Minerals & Chemicals Philipp Corporation) relates to the preparation, from metakaolin, of a novel zeolite having a silicon to aluminium ratio of approximately 1:1, an exceptionally high base exchange capacity, and a very high oil absorption capacity. The zeolite is defined by an X-ray diffraction pattern which is that characteristic of zeolite P. The material contains a relatively high level of titanium impurity (derived from the metakaolin starting material). Suggested uses are for water treatment in the chemical industry and in sugar production, and as a pigment or filler in the production of plastics and rubber goods.
The use of zeolite A in detergent compositions as a carrier for liquid ingredients such as nonionic surfactants has also been disclosed in the art; for example, GB 1 504 211 (Henkel) discloses the use of zeolite A powder as a possible carrier material for nonionic surfactants. EP 149 264A (Unilever) discloses a spray-dried granular material, based on zeolite A, for carrying large loadings of liquid, viscous-liquid, oily or waxy detergent components, for example nonionic surfactants: the resulting "adjuncts" are free-flowing powders.
It has now unexpectedly been found that zeolite MAP, both in powder form and when granulated with or without other materials, is substantially superior to zeolite A as a carrier for liquid, viscous-liquid, oily or waxy detergent ingredients such as nonionic surfactants, allowing the preparation of stable free-flowing powders containing high proportions of such ingredients.